The present invention relates to an ink-jet type image forming device, and more particularly to an ink-jet type image forming device having a suction fan for sucking a print medium (paper) onto a conveyance platen, capable of variably changing the suction force of the print medium as necessary.
Ink-jet type image forming devices include a printer, a plotter, a FAX, and so on. Some of these ink-jet type image forming devices have a fan disposed below the platen to turn the fan during a printing operation to suck a sheet of paper. The fan is provided to prevent the paper sheet from rising and to give a good print quality.
To drive the suction fan, a drive signal is assigned to a CPU port or an ASIC port, and this drive signal is turned on/off to drive the fan.
Actually, however, the suction force of the suction fan need not always be fully (100%) activated during a sequence of print operations. In some situations, the suction force, even if reduced, does not cause any quality problem.
However, the conventional suction fan is simply controlled in such a way that it is either on or off and, therefore, when the suction fan is on, the suction force is always constant (100%). This puts a large load on the paper conveyance motor and, at the same time, causes some power consumption and noise problems.
An image forming device using a roll paper as a print medium cuts the print medium when a print has been finished. At this time, a cut error could occur depending upon the type of a print medium, and this error sometimes causes a jam in cutting the print medium.
In addition, to prevent wet ink from staining a print image, the image forming device waits a while immediately after the completion of a printing until the ink dries, and then cuts the roll paper. This sometimes delays the start of the next printing.
In view of the foregoing, it is an object of the present invention to provide an ink-jet type image forming device that adjusts the suction force of the suction fan to reduce the load of the conveyance motor and, at the same time, to generally reduce power consumption and noise.
It is another object of the present invention to provide an ink-jet type image forming device that adjusts the suction force of the suction fan to prevent a print medium jam from occurring at a cut time.
It is still another object of the present invention to provide an ink-jet type image forming device capable of effectively reducing the time required for the ink to dry by adjusting the suction force of the suction fan.
The ink-jet type image forming device according to the present invention ejects ink from a head onto a print medium being conveyed on a platen to form an image, the head being scanned in a direction substantially at a right angle with a direction in which the print medium is conveyed, the device comprising a suction fan for sucking the print medium from below the platen; and variable-control means for variably controlling a suction force of the suction fan under a predetermined condition.
Thus, the variable controlling of the suction force, instead of simply turning on/off the suction fan, allows the suction fan to be controlled under the predetermined condition. As a result, the load of the conveyance motor is decreased and, at the same time, power consumption and noise are generally reduced.
The variable-control means may be implemented by a number-of-rotation control means for variably controlling a number of rotations of the suction fan. Alternatively, the variable-control means may be implemented by using a flow-path open/close unit disposed in a flow path of air sucked by the suction fan and capable of opening/closing the flow path at a variable open degree.
Preferably, the variable-control means dynamically controls the suction force of the suction fan during a printing operation. For example, the variable-control means has means for checking, during each head scanning, whether or not the head is within a print region ranging from a printing start position to a printing end position, and the suction force of the suction fan is controlled under the predetermined condition in such a way that the suction force of the suction fan exerted when the head is outside the print region is made lower than the suction force exerted when the head is in the print region. Variably controlling the suction force of the suction fan even during a printing operation allows the suction fan to be fine-tuned.
The variable-control means may include means for recognizing a type of the print medium that has been set and the suction force of the suction fan may be controlled according to the type of the recognized print medium. This allows the device to select the suction force suited for the type of print medium, as the predetermined condition.
When the image forming device includes a cutter unit for cutting a roll paper used as the print medium, the variable-control means may use a first suction force and a second suction force as the predetermined condition such that the first suction force is the suction force of the suction fan exerted when one band of printing is being performed by the scanning of the head, and the second suction force is the suction force of the fan exerted when the roll paper is cut by the cutter unit, the second suction force being lager than the first suction force. This increases the suction force of the print medium at a cut time and prevents a cut error and a cut-time jam. In this case, he second suction force of the suction fan may be controlled according to the type of the roll paper.
The image forming device may have a cutter unit for cutting a roll paper used as the print medium, and the variable-control means may maintain the suction force of the suction fan to be strong sufficient to retain a sheet of cut paper for a predetermined period of time even after the cutter unit has cut the roll paper and, after the predetermined period of time has elapsed, change the suction force of the suction fan to such an extent that the sheet of cut paper drops. In this case, the image forming device preferably includes a control means for moving a leading edge of the cut roll paper to a standby position for the next printing, immediately after the cutter unit has cut the print medium. Thus, retaining the sheet of cut paper with the suction fan allows the roll paper to be cut immediately after the completion of printing and, as a result, the leading edge of the roll paper to immediately stand by in the next printing start position. This effectively reduces the ink-drying wait time. Once the leading edge stands by for printing, a printing may be started even during the dry wait time to the extent that the leading edge of the roll paper does not reach the sheet of cut roll paper that is being retained.
The image forming device repeatedly alternates between one-band printing by the scanning of the head and one-band conveyance of the print medium after the one-band printing, and the variable-control means uses a first suction force and a second suction force as the predetermined condition such that the first suction force is the suction force of the suction fan exerted when one band of printing is being performed by the scanning of the head, and that the second suction force is the suction force of the fan exerted when the print medium is conveyed, the second suction force being smaller than the first suction force. This reliably makes the print medium flat during a printing operation, while reducing the conveyance load during the paper conveyance.
In this case and certain cases mentioned above, the suction fan may be rotated and controlled by a fan motor, and the image forming device may have a brake means for suppressing a rotation of the fan motor such that the variable-control means uses the brake means to decrease the suction force of the suction fan. This will enhance the responsibility of the suction force control.